Power supply

ABSTRACT

Circuitry for providing output power for a load such as neon lights, one of the lights being cyclically flashed and the other being constantly illuminated. The circuitry includes separate rectifiers for the two loads, to minimize and virtually eliminate any flicker in the constant portion of the circuit which might otherwise exist incident to the cyclic flashing or interrupting elsewhere in the circuit. The output is desirably at about 20-23 kHz., which is approximately optimum frequency for neon and similar lighting applications, at an initial voltage of about 1600 volts and a running voltage of about 2900 volts for a typical 8-foot neon tube.

United States Patent [72] lnventor Clifford D. Skirvin 2152 Waterby St.. Westlake Village. (aliL 91360 [21] Appl. No. 885,908 [22] Filed Dec. 17,1969 [45] Patented June 15. 1971 [54] POWER SUPPLY 7 Claims, 1 Drawing Fig.

[52] US. Cl 321/4, 315/200. 315/201, 315/253 [51] Int. Cl H02m 5/44, H05b 37/00 [50] Field ol'Seareh 32l/2,4. 27; 315/253, 254, 200 A, 200, 201; 307/96, 132 R, 157

[56] References Cited UNITED STATES PATENTS 3.030.550 4/1962 Smeltzer 315/253 X Primary Examiner William H. Beha, Jr. Attorney- Miketta. Glenny, Poms and Smith ABSTRACT: Circuitry for providing output power for a load such as neon lights, one of the lights being cyclically flashed and the other being constantly illuminated. The circuitry includes separate rectifiers for the two loads, to minimize and virtually eliminate any flicker in the constant portion of the circuit which might otherwise exist incident to the cyclic flashing or interrupting elsewhere in the circuit. The output is desirably at about 2023 kHz., which is approximately optimum frequency for neon and similar lighti'ng applications, at an initial voltage of about 1600 volts and a running voltage of about 2900 volts for a typical 8-fo0t neon tube.

lllllll 'l'l'A'l'l J. a 1/ I: 25 WI";

. PATENTED JUN! 5 I97:

INVENTO/Q tL/FFOED D. SK/EV/N W gl k #JMZ 107' ram/5w.

lllllllllllllllllll POWER SUPPLY BACKGROUND AND SUMMARY OF THE INVENTION In many applications it 15 desirable to energize a plurality of gaseous discharge tubes such as neon lights in such a way as to provide constant illumination for one or more tubes, while flashing one or more other tubes. One illustrative use is in advertising signs; another is warning signs for street and highway use where it may be desirable to constantly illuminate a sign reading Wrong Way, while flashing a sign reading Stop."

In such applications it'is highly desirable that the constantly illuminated sign be maintained at a designed brightness, with preferably no detectable flicker or dimming as a result of the cyclic flashing of the other sign or signs.

The present invention accomplishes this and has for its principal object the provision of a novel power supply to be fed by an ACsource of conventional low frequency and furnishing two output powers for gaseous discharge lighting tubes, one output being'constant and the other being cyclically flashed or interrupted. Other objects and purposes are to provide sucha power supply having an output frequency of about 20 to 23 kI-Iz., which is optimum for many gaseous discharge tubes; to provide such a power supply which may be economically constructed and operated; and for other and additional purposes as'will be understood from a reading of the following description of a preferred embodiment of the invention, taken in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is a schematic diagram of a circuit embodying the present invention.

DETAILED DESCRIPTION Referring now in detail to the drawing showing anillustrative embodiment of the present invention, a transformer indicated generally at includes a primary winding 11 fed from a conventional source of AC power, typically 60-cycle, I20- volt, and so selected as to produce in its secondary winding '12 an output of about 12.8 volts. The output of secondary 12 is fed through leads 14 and 15 to the input of circuitry components shown generally in the upper tier of the drawing, and is also fed to components in the lower tier. The latter provide constant power for a load such as neon light. The former provide intermittent power to a load such as a flashing neon light, and will be first described in detail.

More particularly, the major components of the circuitry shown in the upper tier are enclosed in dotted outline and include rectifying means indicated generally at 20, flasher or interrupter means indicated generally at 40, and inverter means indicated generally at 70. The DC output of rectifying means is cyclically interrupted by interrupter means 40, and then energizes inverter means 70 for producing intermittent AC output power at a frequency of the order of 20 kHz. and a voltage of about, typically, 1600 volts.

Rectifier circuitry 20 is fed by power from leads l4 and 15 through resistor 22 in lead 14, and incoming power is then applied across a rectifier bridge indicated generally at 23 including four diodes 24 arranged in known manner to produce a DC output voltage at vertices 25 and 26. The output power there appearing is conducted through leads 27 and 28 and is filtered in known manner by capacitor 29 and resistor 30 across the output of the bridge. The thus rectified and filtered output is fed through leads 32 and 33 to the input of flasher or interrupter circuitry 40.

Thus. at the input section of interrupter an adjustable resistor 42 and capacitor 43 are connected in series across the input lines 32 and 33. Flasher circuitry 40 includes a pair of reverse blocking triode thyristors, or SCR's, indicated generally at and 60. It will be noted that flasher circuitry 40 will supply power in the output lead 65 only when SCR 60 is conducting. In the usual use of the circuitry of the present invention, it is desirable for the flasher to cycle approximately half of the time on and half of the time off, with a complete cycle lasting approximately 1 second. Thus the remaining elements of the flasher circuitry 40 serve to gate the SCR 60 on and off in accordance with such a cycle.

The junction 41 between adjustable resistor 42 and capacitor 43 is connected through bilateral trigger 44 to gate 51 of SCR 50 and, through capacitor 45, to gate 61 of SCR 60. The anode 52 of SCR 50 is connected through resistor 53 to line 32, and cathode 54 is connected to lead 33. Anode 62 of SCR .60 is connected through capacitor 63 to line 32, and its cathode 64 is connected to line 33. Capacitor 55 interconnects anodes 52 and 62. The output of flasher 40, appearing in lines 65 and 66, is fed to inverter 70.

Means are provided in the input portion of the inventor for isolating the rectifier and flasher from any transients generated in the inverter, and additional conventional over load protection means are also provided in the input portion. Thus line 66 is connected to a diode 71, while line 65 is connected to a thermal circuit breaker indicated generally at 72. A choke 73 and capacitor 74 serve to filter the input between points 75 and 76, whose polarities are positive and negative respectively.

Power appearing at point 75 is fed through line 77 and resistor 78 to the emitter 79 of a double base diode or UJT inprimary winding 89 of an output transformer indicated generally at 90 having a secondary 91 supplying interrupted AC power to output terminals 92 and 93.

lnvertor 70 includes an SCR indicated generally at 94 having its anode 95 connected to line 77 and its cathode 96 connected to point 86 of tank circuit 87. Its gate 97 is connected through line 98 to the output portion of base 82 of UJT 80.

The circuitry shown in the lower tier of the drawing includes rectifying means and inverter means which are respectively identical to the rectifier means 20 and inverter means 70 heretofore described. The circuitry in the lower tier does not include any flasher or interrupter means similar to flasher means 40 in the upper tier of the drawing, since the power supplied by the components in the lower tier is intended to be constant, for constant illumination of a neon light or the like, in contradistinctionto the interrupted power supplied by the components of the upper tier of the circuitry. Within the lower tier, the circuit components and elements are indicated by reference characters lOO greater than the corresponding components and elements shown in the upper tier. Thus, in the lower tier, input leads 114 and 115 supply power from transformer 10 to rectifying means indicated generally at and containing components identical to the components of rectifying means 20 heretofore described. The DC output of rectifying means 120 appears in output leads 132 and 133, which become the input leads for inverter means 170.

In operation, and referring to the circuit components 20, 40 and 70 shown in the upper tier of the drawing, rectified DC in leads 32 and 33 is impressed across resistor 42 and capacitor 43 until the voltage at point 41, between the resistor and capacitor, rises above the breakover voltage of the bilateral trigger 44, and this pulse is supplied to gate 51 of SCR 50, thus turning on that switch and permitting current to flow through resistor 53. This flow of current causes the voltage of point 56 to drop, thus charging capacitor 55 and holding SCR 60 in its off or nonconducting condition.

Once capacitor 55 is charged, however, the gate 61 of SCR 60 will be fired by the next pulse from the trigger 44. SCR 60 will conduct for a period of time determined by the time constant of resistor 53 and capacitor 55. As above-mentioned, the present invention contemplates a flashing cycle of approximately half on and half off, but this ratio can of course be I of this resistance causing an increase of such cycling frequen- The interrupted DC output flasher 40 appears in output leads 65 and 66, which become the input leads of inverter circuitry 70. In line 66 there is provided a diode 71 to isolate the rectifying and flashing circuitry from any transients or other disturbances in the inverter end of the circuit, and the power is filtered by choke 73 and capacitor 74. Desirably there is provided a thermal overload device 72 of conventional construction in the other lead 65.

Power from lead 77 is fed to UJT 80, which serves as a source of oscillation for gating on and d SCR 94. The frequency of pulsing, desirably in the range of 20-23 kl-lz., is determined by the time constant of resistor 78 and capacitor 85. When SCR 94 is gated on, it supplies power to the tank circuit 87, which includes the primary winding 89 of transformer 90, thus generating in known manner the output voltage in secondary winding 91, appearing at output terminals 92 and 93. It will be noted that, each time that SCR 94 is gated on, the voltage therethrough is limited by choke 73, and the reverse voltage generated in primary winding 89 causes SCR 94 to be turned off, being equivalent to a current interruption of that switch.

It will be understood that the operation of the circuit components in the lower tier of the drawing, including rectifier 120 and inverter 170 is identical to that just described in connection with the components of the upper tier, except that no flashing or interrupting of the DC power supplied by rectifier 120 is done.

Illustrative values of the major circuit elements are as follows.

It will be understood that the foregoing values. are illustrative only of operable circuitry, and may be varied within fairly wide limits in accordance with known technology, depending upon environmental parameters, such as load, frequency of flashing desired and the like.

Transformer 90 may have a step-up turn ratio of 7.5:1 and desirably has a ferrite core. Thus the primary may have 100 turns and the secondary 750 turns, desirably pi wound.

Element \alue Resistor 22 5 ohms. 25 watt. Resistor 30 500 ohms, 10 watt. Resistor 42 250K, watt. Resistor 53 l.5K, 10 watt. Resistor 78 5.6K A watt. Resistor 81. 560 ohms, /2 watt. Resistor 83. 1,000 ohms, $6 watt. Capacitor 29. 1.000 mtd.. 25 volts. Capacitor 43. 2 mid.

Capacitor 46 0.1 mfd.

Capacitor 65. 4.0 mt'd.

Capacitor 63- 60 mfd, 50 volts. Capacitor 74- 50 mid, 60 volts. Capacitor 85. 0.0033 mid. Capacitor 88 0.36 mid.

Diode 71 0.3 amp, volts.

I claim: 1. A power supply for neon lights of the like fed from an AC source comprising:

first rectifying means fed by the source for producing a first DC output;

flasher means fed by said first DC output for cyclically interrupting power and producing an interrupted DC output;

inverter means fed by said interrupted DC output for generating an interrupted AC output;

second rectifying means fed by said source for producing a second DC output;

and inverter means fed by the second rectifying means for generating a constant AC output.

2. The invention as defined in claim 1, wherein the AC source has a frequency of 60 Hz.

3. The invention as defined in claim 1, wherein said flasher means interrupts power therethrough at a frequency or about 1 cycle per second.

4. The invention as defined in claim 3, wherein the on time of said flasher means is about one-half of the total time of its cycle.

5. The invention as defined in claim 1, wherein the AC outputs are at a frequency of about 20 to 23 kHz.

6. The invention as defined in claim 5, wherein the AC outputs have initial voltages of about 1600 volts.

7. The invention as defined in claim 6, wherein the AC outputs have running voltages of about 290 volts. 

1. A power supply for neon lights of the like fed from an AC source comprising: first rectifYing means fed by the source for producing a first DC output; flasher means fed by said first DC output for cyclically interrupting power and producing an interrupted DC output; inverter means fed by said interrupted DC output for generating an interrupted AC output; second rectifying means fed by said source for producing a second DC output; and inverter means fed by the second rectifying means for generating a constant AC output.
 2. The invention as defined in claim 1, wherein the AC source has a frequency of 60 Hz.
 3. The invention as defined in claim 1, wherein said flasher means interrupts power therethrough at a frequency or about 1 cycle per second.
 4. The invention as defined in claim 3, wherein the on time of said flasher means is about one-half of the total time of its cycle.
 5. The invention as defined in claim 1, wherein the AC outputs are at a frequency of about 20 to 23 kHz.
 6. The invention as defined in claim 5, wherein the AC outputs have initial voltages of about 1600 volts.
 7. The invention as defined in claim 6, wherein the AC outputs have running voltages of about 290 volts. 